Create a visible shelf and constrain window movement

ui/aura_shell/launcher/launcher.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/aura_shell/launcher/launcher.h"
 
 #include "ui/aura/window.h"
 #include "ui/aura_shell/launcher/launcher_model.h"
 #include "ui/aura_shell/launcher/launcher_view.h"
 #include "ui/aura_shell/shell.h"
 #include "ui/aura_shell/shell_delegate.h"
 #include "ui/aura_shell/shell_window_ids.h"
 #include "ui/gfx/compositor/layer.h"
 #include "ui/views/widget/widget.h"
 
 namespace aura_shell {
 
 Launcher::Launcher(aura::Window* window_container)
     : widget_(NULL),
       window_container_(window_container) {
   window_container->AddObserver(this);
 
   model_.reset(new LauncherModel);
 
   widget_ = new views::Widget;
   views::Widget::InitParams params(views::Widget::InitParams::TYPE_CONTROL);
-  // All the content is drawn by the launcher buttons. Turn off the widget's
-  // layer's texture to avoid unnecessary memory use.
-  params.create_texture_for_layer = false;
+  params.create_texture_for_layer = true;
+  params.transparent = true;
   params.parent = Shell::GetInstance()->GetContainer(
       aura_shell::internal::kShellWindowId_LauncherContainer);
   internal::LauncherView* launcher_view =
       new internal::LauncherView(model_.get());
   launcher_view->Init();
   params.delegate = launcher_view;
   widget_->Init(params);
   gfx::Size pref = static_cast<views::View*>(launcher_view)->GetPreferredSize();
   widget_->SetBounds(gfx::Rect(0, 0, pref.width(), pref.height()));
   widget_->SetContentsView(launcher_view);
@@ skipping 50 matching lines @@
     model_->RemoveItemAt(i - model_->items().begin());
 }
 
 void Launcher::OnWindowVisibilityChanged(aura::Window* window,
                                          bool visibile) {
   if (visibile && !known_windows_[window])
     MaybeAdd(window);
 }
 
 }  // namespace aura_shell